Print hammer drive mechanism for high-speed printers



15, 19.67 G. SCHACHT ETAL 3,335,659

PRINT HAMMER DRIVE MECHANISM FOR HIGH SPEED PRINTERS Filed July 29,1964 1 j '3 Sheets-Sheet 1 FIG. 1

INVENTORS TORNEY Augl5,' 9 G. SCHACHT ETAL PRINT HAMMER DRIVE MECHANISM FOR HIGH SPEED PRINTERS Filed July 29, 1964 3 Sheets-Sheet 2 Aug. 15, 1967 PRINT HAMMER Filed July 29,, 1964' G..$CHACHT ETAL 3,335,659

DRIVE MECHANISM FOR HIGH SPEED. PRINTERS a Shets-Sheet 5 FIG. 3

United States Patent 3,335,659 PRINT HAMMER DRIVE MECHANISM FOR HIGH-SPEED PRINTERS Guenter Schacht, Boblingen, and Eberhard Spieth, Holzgerlingen, Germany, assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed July 29, 1964, Ser. No. 385,914

Claims priority, application Germany, Aug. 24, 1963,

Claims. (Cl. 101-93) This invention relates to printing and particularly to an electromagnetically operated print hammer drive mechanism for high-speed printers.

High-speed mechanical printers, of the type used especially for output units in information processing machines, generally contain a number of print mechanisms corresponding to the number of printing positions in a printed line. Each of said print mechanisms, the print hammers of which are arranged in a row corresponding to the line to be printed, has presented thereto all of the occurring characters, which may be arranged, e.g., on a type chain, a type roller or a type bar, at least once during each machine cycle. Whenever the electric image of a character then in the position for printing corresponds with the respective information stored in the data processing machine, the print mechanism at such printing position is actuated.

For the purpose of driving the print hammers of such printing mechanisms it is known to transmit to the print hammer kinetic rotary energy through a thrust gear, e.g., or potential energy stored in a tensioned spring. Also known are electromagnetically operated print hammer drive mechanisms in which the source of energy and the electromagnetic actuating means are integrated in one component. Print hammer drive mechanisms of the latter type are so designed that the armature of an electromagnet accelerates the print hammer, mostly through a lever arrangement.

In the known print hammer drive mechanisms of this latter type the disadvantage arises that there is always at least one pivoted lever through which the traction of the magnet is transmitted as a percussive force to the print hammer. Irrespective of the energy losses caused thereby, the assembly of pivoted parts also causes difficulties in solving the problem of accommodating the great number of individual print hammer drive mechanisms in a tightly packaged arrangement, so that the individual print hammer drive mechanisms cannot be fabricated with the desired small size and, therefore, have to be assembled in an interleaved fashion.

The print hammer drive mechanism of this invention avoids the aforementioned disadvantages due to the provision that the print hammer, which is mounted to be movable in the longitudinal direction, itself forms the magnet armature of the print magnet operating it, and that the print magnet is arranged so that its magneic field exerts on the prime hammer a force directed toward the printing position.

A particularly advantageous embodiment of the print hammer drive mechanism according to this invention results when theprint magnet is arranged laterally of the print hammer and the polar surfaces of the magnet yoke and of the armature yoke arranged on the print hammer facing each other are so inclined with respect to the axis of the print hammer that, in addition to the force decreasing with the hammer path increasing, by shortening of the lines of force a force component in the direction of movement is obtained which, as a result of the lines of force extending diagonally with respect to the hammer axis between the polar surfaces, increases with the hammer path 3,335,659 Patented Aug. 15, I967 "ice increasing. In this connection, it has proved to be of special advantage to provide a plurality of magnet yokes which are serially aligned in the axial direction with their associated armature yokes, and the magnet coil is distributed among the individual magnet yokes, so that, in conjunction with the bar-shaped design of the print hammer serving as an armature and with the well-known pivotless support of the print hammer on two leaf springs, a particularly fiat, disk-shaped structure of the print hammer drive mechanism is obtained.

To particular advantage, the print hammer drive mechanism of this invention may, at the same time, be used for damping the hammer return movement after the type impact. In accordance with this invention, that is achieved by providing that the current pulse causing the energization of the print magnet is of such a tuned length that for the duration of the return movement of the print hammer the energization of the print magnet is maintained entirely or in part within a predetermined period of time. That may be obtained in a simple manner by the provision that the pulses simultaneously energizing the individual partial magnets of the print magnet are of differential lengths.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 schematically illustrates a side view of the print hammer drive mechanism according to this invention;

FIG. 2 shows the same view as FIG. 1 however at the movement of the printing impact, and

FIG. 3 also schematically represents a type cylinder printer in perspective, illustrating the print hammers arranged in a row at the individual printing positions together with the drive mechanisms of said print hammers.

Referring to FIG. 1 of the drawings, the print hammer drive mechanism is represented therein in its inoperative position. The reference numeral 10 designates the print hammer which consists of a bar having a rectangular cross-section and which carries the hammer head 11 on its front end. The print hammer is mounted on two vertical leaf springs 12, 13 which in turn are clamped in position in a base member 14. Thus, the print hammer 10 is movable in parallel to its longitudinal axis. For printing a character the print hammer 10 strikes the sheet of paper 15, behind which an inking ribbon 16 is placed, against the continuously rotating type cylinder 17 on which the characters to be printed are arranged in relief. The return movement of the print hammer 10 is limited by a buffer stop 18 having a mass approximately equal to that of the print hammer and clamped in a stationary position by means of an elastic separator 19 attached to a base member 20.

In accordance with this invention the print hammer 10 is designed to serve at the same time as the magnet armature of the print magnet 21 which operates it. The print hammer consists of hard steel difficult to magnetize and carries two soft magnetic U-shaped armature yokes 22, 23. The print magnet 21 which is fixedly mounted on base member 24 and is arranged laterally of the print hammer 10, is provided with two U-shaped magnet yokes 25, 26, which are arranged one behind the other as seen in the longitudinal direction and the free legs of which face the poles of the armature yokes 22, 23 mounted on the print hammer 10. This structure of the print magnet 21 with a plurality of magnet yokes 25 and 26 insures an especially fiat, disk-shaped configuration of the print hammer drive mechanism. Of the over-all magnet coil, only relatively few turns are allotted to each individual yoke which take up only little space. Moreover since it is unnecessary to provide any bearings for pivoted parts, it is insured by means of the above-described arrangement of the print magnet 21 together with the bar-shaped configuration of the print hammer and its support on .two leaf springs 12 and 13 that the overall print hammer drive mechanism does not exceed the width of one printing position.

In operation, the magnet field of print magnet 21 exerts a. force on the print hammer 10 in the direction toward the printing cylinder 17. This force is, on the one hand, due to the fact that the magnetic lines of force attempt to shorten in the circuit closed through the armature yoke 21. This force is greatest with the armature having its greatest deflection in the inoperative position. It decreases continuously with the hammer path increasing until the pole shoes 22 and 23 of the armature are exactly below the poles of the magnet yokes 25 and 26. However, in the arrangement of this invention this force has superimposed thereon a second force which is caused by the fact that the polar faces 27, 28 of the magnet yokes 22 and 23 and of the armature yokes 2S and 26 respectively are inclined with respect to the armature axis. The lines of force which extend vertically between the polar surfaces facing each other but are inclined with respect to the print hammer axis produce an additional force component in the horizontal direction which increases with the increasing hammer path while at the same time the air gap decreases. By superimposing these two forces it is possible to obtain an approximately constant pushing force along the hammer path. The vertical components of the magnetic forces exert a pulling force on the print hammer 10. They insure that the leaf springs 12, 13 supporting the print hammer remain stretched during the hammer movement and do not begin to flutter.

A special advantage of the above-described magnet system resides in the fact that it is also possible in a simple manner to achieve an additional damping of the print hammer 10 during its return movement after the printing impact. This is accomplished by providing a current pulse for energizing the print magnet 21 which is maintained during the return movement of the print hammer 10 entirely or partly over a certain period of time. The forced change in the magnetic flux occurring in that process results in a reduction of the kinetic energy of the rapidly returning hammer. The partial maintenance of the magnet energization for damping may, e.g., be effected by energizing the magnet coils 29, 30 by two different pulses 3'1, 32 which, while they are initiated at the same time, are of different lengths.

In order to effect additional accelerations and damping, the armature yokes 22 and 23 on the print hammer 10 may also be designed as permanent magnets. For that purpose, they are preferably arranged in such a fashion that the poles of the magnet yokes 25 and 26 are respectively faced by opposite permanent magnet poles 22 and 23, respectively.

The print hammer drive mechanism of this invention may be mounted both in print units using a type drum and in printers employing a type chain or a type bar. As an illustrative example, FIG. 3 shows a type cylinder printer in which, in a row corresponding to a line to be printed, a print hammer It with its associated drive mechanism is provided for each printing position.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A print hammer mechanism for a high speed printer comprising in combination,

(a) a print hammer member,

(b) means for supporting said hammer member for movement along a predetermined path from a rest 4 position to a print position on impact with a type carrier or the like,

(c) operator means for impelling said hammer from said rest position to said impact position whereby said hammer produces an imprint on a print medium or the like and rebounds toward said rest position comprising (d) a first magnetic core means comprising a U-shaped magnetic core member having spaced apart polar faces along the path of the hammer fixedly located proximate and to one side of said path,

(e) a second magnetic core means comprising a U- shaped magnetic core member having correspondingly spaced apart polar faces along the hammer movable with said print hammer,

(f) said first and second core means forming a magnetic circuit including variable air gaps defined by the polar faces of said U-shaped magnetic core members,

(g) means for generating a magnetic field in said magnetic circuit and across said air gaps including coil means magnetically coupled with at least one of said core means, and means for energizing said coil means for alternately impelling said hammer means to said imp-act position and for damping said hammer movement or rebound toward said rest position.

2. A print hammer mechanism in accordance with claim 1 in which (a) said support means comprises a base member and cantilever spring means supported therefrom, said spring means being deflectable in the direction of said predetermined path,

(b) said hammer member comprises an elongate bar attached to said spring means, said bar being movable on said spring means with the longitudinal axis of said bar substantially parallel with said predetermined path,

(c) said first and second magnetic core means comprising magnetic cores having pole faces diagonal to said predetermined path,

(d) and said energizing means produces a magnetic field between said pole faces having force components transverse to and coaxial vw'th s aid path.

3. A print hammer mechanism in accordance with claim 1 in which (a) said second magnetic core means comprise U- shaped permanent magnets attached to said print hammer member.

4. A print hammer mechanism in accordance with claim 1 in which (a) said means for generating a magnetic field in said magnetic circuit includes coil means wound about said first magnetic core means, and

(b) said means for energizing said coil means includes a means for generating an energizing pulse of a duration for both impelling said hammer means to said impact position and for damping said hammer element motion on rebound toward said rest position.

5. A print hammer mechanism in accordance with claim 1 in which (a) said first magnetic core means comprises a pair of electromagnet cores serially aligned along said predetermined path,

(b) said second magnetic core means comprises a pair of magnetic hammer cores serially aligned on said print hammers,

(c) said electromagnet cores and said hammer cores forming individual mutually assisting magnetic circuits including variable air gaps which slope toward the print hammer member in the direction of hammer motion toward the print position,

((1) and means for generating a magnetic field in said magnetic circuits including means for energizing said pair of electromagnet cores simultaneously with pulses for impelling said hammer means to said impact position and for pulsing one of said electromag- 5 6 net cores for damping said hammer movement on re- 3,172,353 3/ 1965 Helms 101-93 bound toward said rest position. 3,195,453 7/1965 Thiemann 10 1-93 References Cited ROBERT E. P-ULFREY, Primary Examiner. UNITED STATES PATENTS 5 DAVID KLEIN, Examiner. 2,843,243 7/ 1958 Masterson 101-93 X P. R. WOODS, Assistant Examiner.

2,997,632 8/1961 Shepard 10193 X 

1. A PRINT HAMMER MECHANISM FOR A HIGH SPEED PRINTER COMPRISING IN COMBINATION, (A) A PRINT HAMMER MEMBER, (B) MEANS FOR SUPPORTING SAID HAMMER MEMBER FOR MOVEMENT ALONG A PREDETERMINED PATH FROM A REST POSITION TO A PRINT POSITION ON IMPACT WITH A TYPE CARRIER OR THE LIKE, (C) OPERATOR MEANS FOR IMPELLING SAID HAMMER FROM SAID REST POSITION TO SAID IMPACT POSITION WHEREBY SAID HAMMER PRODUCES AN IMPRINT ON A PRINT MEDIUM OR THE LIKE AND REBOUNDS TOWARD SAID REST POSITION COMPRISING (D) A FIRST MAGNETIC CORE MEANS COMPRISING A U-SHAPED MAGNETIC CORE MEMBER HAVING SPACED APART POLAR FACES ALONG THE PATH OF THE HAMMER FIXEDLY LOCATED PROXIMATE AND TO ONE SIDE OF SAID PATH, (E) A SECOND MAGNETIC CORE MEANS COMPRISING A USHAPED MAGNETIC CORE MEMBER HAVING CORRESPONDINGLY SPACED APART POLAR FACES ALONG THE HAMMER MOVABLE WITH SAID PRINT HAMMER, (F) SAID FIRST AND SECOND CORE MEANS FORMING A MAGNETIC CIRCUIT INCLUDING VARIABLE AIR GAPS DEFINED BY THE POLAR FACES OF SAID U-SHAPED MAGNETIC CORE MEMBERS, (G) MEANS FOR GENERATING A MAGNETIC FIELD IN SAID MAGNETIC CIRCUIT AND ACROSS SAID AIR GAPS INCLUDING COIL MEANS MAGNETICALLY COUPLED WITH AT LEAST ONE OF SAID CORE MEANS, AND MEANS FOR ENERGIZING SAID COIL MEANS FOR ALTERNATELY IMPELLING SAID HAMMER MEANS TO SAID IMPACT POSITION AND FOR DAMPING SAID HAMMER MOVEMENT OR REBOUND TOWARD SAID REST POSITION. 